Some 10 years after analysts at Goldman Sachs coined the acronym BRICs, tying Brazil, Russia, India and China into a single investment theme, the concept is beginning to look distinctly flakey.

That's not to say Goldman's original forecasts have been proved wrong. In fact, they turned out to be quite accurate.

Back in 2003 Goldman's economists came up with long-term growth projections for the BRIC countries as well for as the G6: the US, Japan, Germany, Britain, France and Italy.

As the first chart shows, they didn't foresee the 2008 crisis. But apart from that, if anything their forecasts for the emerging economies were too modest.

They predicted that China would overtake Japan to become the world's second-biggest economy in 2016. In fact, China leapfrogged Japan six years earlier in 2010.

And today, their forecast that China will catch up with the US by 2041 looks positively limp-wristed. This week a collection of US intelligence agencies warned that China would eclipse the US by 2030. Many economists believe it will happen by 2020.

In relative terms, however, Goldman's analysts got things more or less right. They said that between 2001 and 2011 the BRICs would grow from 13 per cent of G6 GDP to 23 per cent in constant US dollar terms. In fact, the BRICs reached 26 per cent of G6 GDP.

Not everyone believes those original forecasts will prove so accurate from here onwards, however. Some analysts, notably at Goldman's rival, Morgan Stanley, argue that the growth surge in emerging economies over the last 10 years was the result of a once-in-a-lifetime influx of liquidity, propelled by rock-bottom interest rates in the developed world.

Over the coming years that tide will recede. As a result, the synchronised rapid growth of the last 10 years is unlikely to continue.

Sceptics warn that China's investment and export-led growth model is broken, and that with debt levels now exceeding 200 per cent of gross domestic product, bad debts will weigh heavily on growth over the coming years.

Meanwhile, India will struggle to maintain rapid real growth rates unless the government can succeed in containing its ballooning deficit.

Brazil, too, faces fiscal problems, with government taxes and social spending that have reached European levels, crowding out badly needed private investment. If the commodity bull market now runs out of steam, as many fear, growth could stall.

A commodity bust would also severely undermine growth in Russia, where the economy lacks a foundation of small entrepreneurial private companies to drive future development.

Goldman's original forecasts did allow for a slowdown in growth. Back in 2003 its analysts foresaw China's growth rate easing to an average 5 per cent a year between 2015 and 2020. They also expected growth to slow in Brazil and Russia.

But the real reason the BRICs concept looks increasingly flakey has nothing to do with outright economic growth rates.

The trouble is that it no longer stands up as an investment theme.

The whole idea was that faster growth in the big emerging markets would generate superior returns to investors - far better than they could hope to earn in the developed world.

That worked between 2002 and 2007, when investors did indeed make handsome gains in the BRIC markets.

But since then the BRIC markets have crumbled. The second chart shows total returns to a US dollar investor from BRIC stock markets over the last five years. China and Brazil have both lost around 20 per cent. India is down 30 per cent, and Russia has plunged 43 per cent.

Over the same period, the US stock market has provided positive returns of 8 per cent.

That leaves BRICs looking like an investment theme well past its sell-by date.